1. Field of the Invention
The present invention relates to a sweetener which has a high sweetness intensity and excellent sweetness quality and also contains, as a main component, rebaudioside A and β-1,4-galactosyl rebaudioside A which are useful as sweeteners for various foods and drinks, and to a process for producing the same.
2. Description of Related Art
Heretofore, sugar (sucrose) has widely been used as a sweetener for foods and drinks. In particular, coffee drinks, including canned coffee, and carbonated beverages contain large amounts of sugar. Recently, because of the trend of increasing interest in health and low calorie foods and drinks, there is a tendency for ingestion of sugar, which can cause obesity, diabetes, and dental caries, to be reduced, and a sweetener having a high sweetness intensity is replaced by sugar.
Such a sweetener having a high sweetness intensity is a Stevia sweetener derived from an extract of a perennial plant, of the aster family, originating in Paraguay, South America, for example, Stevia rebaudiana BERTONI.
A Stevia sweetener obtained from the extract of Stevia plants (hereinafter referred to as a Stevia extract) has a sweetness, which is hundreds times stronger than that of sugar, but has a characteristic that the sweetness sensation is produced more slowly than that of sugar, that is, the so-called “head-taste of the sweetness” is delayed, and also has a characteristic that the sweetness remains comparatively longer, that is, so-called “after-taste of sweetness” is prolonged. When using a large amount of stevioside contained in the Stevia sweetener in coffee drinks and carbonated beverages, consumers clearly experience discomfort because of a peculiar astringency and bitter after-taste, in addition to the sweetness.
Therefore, various research has been conducted to improve the sweetness quality of the Stevia sweetener. For example, Japanese Unexamined Patent Application, First Publication No. Sho 58-094367 discloses a process for preparing a sweetener containing, as a main component, β-1,4-galactosyl stevioside resulting from the β-1,4 bonding of a galactosyl group to stevioside, which comprises allowing a β-1,4-galactosyl transferase to react on an aqueous solution containing a Stevia extract containing stevioside as a main component and a β-1,4-galactosyl sugar compound.
According to this process, the sweetness is improved to become a mild sweetness and the prolonged after-taste of sweetness is relatively improved, and also the bitterness and astringency are reduced, while the effect of improving the sweetness quality is not sufficient, and the resulting sweetener is still insufficient for use in coffee drinks and carbonated beverages.
Also, Japanese Unexamined Patent Application, First Publication No. Hei 9-107913 discloses a process for the α-addition reaction of glucose to a Stevia extract containing rebaudioside A as a main component. However, there arose a problem in that the enzyme reaction proceeds to form a long glucose chain from glucose added to rebaudioside A, thus reducing sweetness intensity of the resulting α-glucosyl rebaudioside A by about 45% as compared with rebaudioside A.
As described above, the sweetness quality of a conventional sugar-added Stevia sweetener is improved to some extent by the addition of sugar, while the sweetness intensity is reduced and defects peculiar to the Stevia sweetener, for example, the delayed head-taste of sweetness as well as an after-taste with bitterness and astringency are not completely improved, and thus consumers feel discomfort when using the Stevia sweetener in coffee drinks and carbonated beverages.